1. Field of the Invention
The present invention relates to a safe heater, especially to a heater with an enclosing envelope to enhance the safety thereof.
2. Description of the Prior Art
The advanced heater generally uses ceramic resistor material (PTC) and uses thermal radiation to transmit heat energy to ensure safety. The PTC heater comprises a flat main body with two surfaces (upper surface and lower surface), an anode and a cathode are formed on the two surfaces, respectively. The upper surface and lower surface are used as electrodes and function as heat emitting surfaces. However, the size of the flat main body is small such that heat guiding means such as heat-dissipating plates are required to guide the thermal energy. The heat-dissipating plates are generally fin-shaped metal plates for efficient heat exchange. Moreover, the heat-dissipating plates generally require supporting means such that the heat-dissipating plates abut vertically against the upper and lower surfaces of the flat PTC main body. The flat PTC main body is generally exposed to the external environment, and is probably exposed to moisture. The main body is flat shape with thin thickness, the flashover between the anode surface (upper surface) and the cathode surface (lower surface) of the main body is small. A spark may be generated when an inrush of current occurs. Moreover, flock and wasted paper beside the heater may cause a blaze due to the spark.